1. Field of the Invention
The present invention generally relates to system and method for measuring interferences.
2. Description of the Prior Art
SEM (Scanning electron microscope) is expensive to buy and maintain. It is dynamic rather than static in its operation: requiring extremely stable high-voltage supplies, extremely stable currents to each electromagnetic coil/lens, continuously-pumped high-/ultra-high-vacuum systems, and a cooling water supply circulation through the lenses and pumps. As it is very sensitive to vibration and external magnetic fields, microscopes aimed at achieving high resolutions must be housed in buildings (sometimes underground) with special services.
However, the AFM (Atomic Force Microscope) has several advantages over the scanning electron microscope (SEM). Unlike the electron microscope which provides a two-dimensional projection or a two-dimensional image of a sample, the AFM provides a true three-dimensional surface profile. Additionally, samples viewed by AFM do not require any special treatments (such as metal/carbon coatings) that would irreversibly change or damage the sample. While an electron microscope needs an expensive vacuum environment for proper operation, most AFM modes can work perfectly well in ambient air or even a liquid environment. This makes it possible to study biological macromolecules and even living organisms. In principle, AFM can provide higher resolution than SEM.
Nevertheless, a disadvantage of AFM compared with the scanning electron microscope (SEM) is the image size. The SEM can image an area on the order of millimeters by millimeters with a depth of field on the order of millimeters. The AFM can only image a maximum height on the order of micrometers and a maximum scanning area of around 150 by 150 micrometers. Another inconvenience is that at high resolution, the quality of an image is limited by the radius of curvature of the probe tip, and an incorrect choice of tip for the required resolution can lead to image artifacts. Traditionally the AFM could not scan images as fast as an SEM, requiring several minutes for a typical scan, while an SEM is capable of scanning at near real-time (although at relatively low quality) after the chamber is evacuated. The relatively slow rate of scanning during AFM imaging often leads to thermal drift in the image (Lapshin, 2004, 2007), making the AFM microscope less suited for measuring accurate distances between artifacts on the image.
Hence, a system and method for measuring interferences of the present invention is disclosed for solving the above-mentioned problems.